System of electrically transmitting signs.



H. HOFFMANN.

SYSTEM OF ELEGTRICALLY TRANSMITTING SIGNS.

YAPPLICATION FILED ocr. 21, 1914.

1,142,572. Patented June 8, 1915.

2 SHEETS-SHEET IHE NORRIS PETERS CD., PHOTO-LITHQ. WASHINGTON. D. C-

H. HOFFMANN.

SYSTEM OF ELECTRICALLY TRANSMITTING SIGNS. APPLICATION FILED OCT- 21. 1914.

13,142,572. Patented June 8, 1915.

2 SHEETS-SHEET 2. v

Fly. 2

THE NORRIS PETERS 50., PHOTO-LITHQ, WASHINGTON, D. C.

UNITED stares PATENT orrrcn,

HERMANN HorrMAriN, or BREMEN, GERMANY, ASSIGNOR To THE FIRM or TELEPAN'TOGRAPH GEsELLsoHAF'r BBEMEN, GERMANY.

MIT BESGHRANKTEB HAFTUNG', OF

svs'rsn or ELEcrmoALLv V TRANSMITTING SIGNS.

To all'whom it may concern Be it known that I, HERMANN HQFFMANN, engineer, a subject of the GermanEmperor, residing at 80 Yorkstrasse, Bremen, Germany, have invented certain new and useful Improvements in Systems of Electrically in which the return conductor for the elec-.

tric current is provided by the ground. .In such systems the operation of the receiving apparatus is frequently interfered with by foreign currents coming from the earth 'which is frequently overcharged'with foreign currents, particularly near electrical central stations or largecitles. Therefore the receiving apparatus are affected not only by the current impulsescoming from the sender, but also by earth currents, so that the transmission of the signs is disturbed.

The object of the improvements is'to .provide a system in which this objection is re moved.

With this object in view my invention consists in providing means in connection with the system whereby the effect of the foreign currents on the receiving apparatus is compensated.

For-the purpose ofexplaining the invention several examples embodying the same have been shown "in the accompanying drawing, in which- Y 3 Figures 1 to 3 show diagrams of electrical connections between the sender and receiver, the latter being represented'only by electrical coils. Q e

The sender and receiver may be of any known or preferred constructions, and they have not been illustrated in detail, because 7 my invention does not relate to the construction ofthese parts.

In the example shown in Fig. 1 apart from theconductor provided by the earth Specification of Letters Patent.

. components.

Patented June s, 1915.

' Application filed October 21, 1914. Serial No. 867,843.

combination of the third conductor with the earth connection the. effect of the foreign currents coming from the earth can becoma third conductor is provided, and by the V pensated, so that the current impulses coming from thesender are not disturbed. In

the said-figure, the sign transmitting resistances provided in the sender have been indicated by the numerals 1 and 2, and to the 7 said resistances electric energy is supplied from a battery5. -=At one endthe said resistances are connected by a conductor 11 to the earth -at 16 and to a common return wire 10. From the points 3 and 1 the sign transmitting currents are taken in any known orpreferred way, which currents are I conducted through wires 6 and 7 to-receii ing'members 8 and 90f any known or preferred construction, the common return conductor 10' and the earth at 17 being conand which have the same, electrical strength as the coils12 and 13. The coils 1 1 and 15 are preferably connected in series, and the conductors 6, 7 and 10'can be brought into harmony by resistances 18, 19, and 20. i i

The 'currentscoming from the earth pass through the conductors" 6, 7 and. 10 in the' same; direction-and at equal strength,"for

example" in the direction of the arrows shown in the Fig. 1. 'Therefore all the coils 12,-1-1 and 13, 15'of theelements 8, 9 are traversed by the same current coming from.

the ground, though the direction and the the coils of each apparatus are wound in opposition to each other. -'Therefore the current coming from the earth hasno influence on theelement's 8 and 9. On the other hand, the larger part of the current impulses coming from the sender for transmitting the signs to the receiver flows over thecoils 12, 13, and ground 17, 16, while a small part only flows'through thecoils 14,

15 and wire 10. V The resistance of the earth is very small, say from 5 to 20 ohms, and

practically-it 'does not aflect'the current The resistance of the conductor 10 is much higher, and to this resistance the resistance of the coils 14 and 15 ing effect on the current impulses from the sender is avoided.

In the examples shown in Figs. 2' and 8 the return conductor is provided exclusively by the earth. To avoid the injurious effect of the currents coming from-the earth on the receiving apparatus bridging coils of comparativel small resistances are connected in shunt with the circuits of the receiving elements. a I

As shown in Figs. 2 and 3 the resistances of the sender have been indicated by the numerals 1 and 2, and 1 and 2, and the current is supplied to the resistances from batteries 5 and 5 respectively, Oneside of the resistances is connected to the earth at 1 6 and 16 over a wire 11' and 11 respectively, The sign transmittingcurrent impulses are taken fromthe points 3 and 3 and 4; and 4 respectively, and the said currentimpulses are conducted through wires 6, 'Z and 6", 7 respectively to receiving elements 8, 9 and 8, 9 of any known or preferred construction, the coils 12', 13' and 12", 13" of the receiving elements being connected to the earth at 17 and 17.

In the construction shown in Fig. 2 the coils 12 and" 13 have comparatively high resistances Small resistances 21 and 22 respectively are connected n shunt to the Stud coils, the said resistances being say one fifteenth to, one twentieth of that of the coils 12 and 13; For example, if the resistance of the coils 12 and 13 is about 3000 ohms each,,the resistance of the coils 21 and 22 is about 150' ohms each or less. But I wish it to be understood, that these values may be different according to practical conditions, provided the resistances 21 and 22 are sufficiently small as compared to the coils 12 and 13; I V A r a I Experience has shown, that the intensity of the earth currents is very small, the maximum being a few milli-amperes. Therefore practically almost the whole amount of theseweak earth currents will pass over the small resistances 21 and 22, and they will have no effect in the coils 12' and 13 of the receiying apparatus, because the amount of the current is too small. v

Itwill be understood that the voltage of the battery located in the sender must be so strong,'that to thec oils 127 and 13 an amount, of current is supplied which is sufficient for transmitting the signs. I a

The example shown in 3 is to be preferred, if the system currents areinfluenced not only by earth currents but also by induction currents of neighbored electric systems. In such cases besides the bridged resistances 21 and 22 I insert resistances 23 and 24 before the instrument coils 12" and 13 so that the latter can be regulated with re 'a-rd to the writing currents only.

\Vhile in describing the invention reference has been made to'compensating the inj'u'rious effect of currents coming from the earth, it will readily be understood, that the same arrangement may be used for avoiding the effect of induced currents. In this case, in the arrangement shown in Fig. 1 all the three conductors are uniformly induced, so that the compensating coils compensate this induction.

In the examples shown in Figs. 2 and 3 the said induced currents would directly be conducted to the earth through the bridges 21 and 22 and 21" and 22 respectively, and as the said induced currents are comparatively weak, alsothese examples relate to avoiding the injurious eifect of the induced currents. V V

I claim herein as myinvention: I: j 7

1. A system for electrically transmitting signs, comprising a sender adapted to send two current impulses, anda receiver comprising two electromagnetic coils electrically connected with the sender for receiving each one of the impulses and through theearth as a return conductor, and compensating coils one for each of said electromagnetic coils arranged to compensate the eifect of the earth currents passing through the electromagnetic coils.

2. A system for electrically transmitting signs comprising a sender adapted to send two current impulses and a receiver comprising two electro-magnetic coils electrically connected with the sender for receiving each one of the impulses and through the earth as a return conductor, and bridging conductors connected in shunt relation with. said electro-magnetic coils, the electrical resistance ofthe bridgingconductors being so small as compared to the resistance of the electro -magnetic coils and associated part of the circuit that the part of the earth current which flows through the electro-magnetie coils has practically no eiiect on the recelver. V j a,

A system for electrically transmitting signs, comprising a sender adapted to send two impulses, and areceiver comprising two electromagnetic coils electrically connected with the sender for receiving each one of the impulses and through the earth as return conduct r, and bridging conductors one for each of the, electromagnetic coilsv and connected in shunt therewith, the electric rei an of he br d n .wnd ew being so small as compared tothe resistances of the v electromagnetic coils and associated parts of the circuit that the parts of the earth current which flow through the electromagnetic coils have practically no effect onthe receiver.

4. A system for electrically transmitting signs, comprising a sender, and receiver comprising at least one electromagnetic coil, and an additional resistance in series therewith said sender and receiver being included at least in one circuit comprising as a return circuit the earth, and a bridging conductor connected in shunt to the electromagnetic coil and resistance, the electrical resistance of the bridging conductor being so small as compared to the resistance of the electromagnetic coil and resistance that the part 15 of the earth current which flows through the electromagnetic coil has practically no effect on the receiver.

In testimony whereof I have affixed my signature, in presence of two witnesses.

HERMANN HOFFMANN. Witnesses:

KARL GAILSE, FREDERICK HOYERMANN.

Copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents,

- Washington, D. 0. 

